This BMW 320d EfficientDynamics is the cleanest, greenest, most fuel-efficient 3-series ever. It’s designed to appeal to fleet buyers and the environmentally conscious alike, and thanks to some further tuning and tweaking of the company’s biggest selling Three, the 320d EfficientDynamics will, on paper at least, achieve 68.9mpg and emit a remarkable 109g/km. It’ll be officially unveiled at the Frankfurt motor show next month, but CAR has already driven it…

So this is a BMW 320d Efficient Dynamics? But I thought Efficient Dynamics was standard?

It is – since BMW first revealed its eco-friendly Efficient Dynamics technology in 2007, every manual 320d that’s emerged from Munich’s factories has been fitted with active aero, low-rolling resistance tyres, a gearshift indicator, an intelligent alternator and a stop/start system. In fact, every four-cylinder Three with a manual ‘box has come so equipped.

But there’s now a new version. So far the Efficient Dynamics tech has all been standard and relatively under-the-radar (whereas Mercedes badges all its latest models BlueEfficiency) but BMW has now come up with an even cleaner 3-series. It’s the company’s special eco model, with extra tweaks to make it even greener and save you money with its startling CO2 output.

So what are the important changes?

The four-cylinder diesel is the familiar single-turbo 2.0-litre unit that powers that 316d, 318d and 320d, but some engine tweaks lower the power (and thus the CO2 output), but the torque output is actually up. The usual complement of Efficient Dynamics tech is standard, but this 320d has a longer final drive ratio, new 16-inch ‘Aero’ alloys and lower suspension.

Beyond that there’s a new two-mass flywheel with a centrifugal-force pendulum – it sounds complicated but effectively weights inside the flywheel counteract the vibrations from the engine. In itself this doesn’t improve emissions but the system is claimed to make the driving experience smoother at lower rpm, which should in turn encourage drivers to use fewer revs and higher gears. And that’s means more miles per gallon.

But the end result isn’t an efficient-but-achingly-slow BMW. After all the tweaking this 320d puts out 161bhp and 265lb ft, respectively down and up on the regular 177bhp/258lb ft 320d. Plus the on-paper performance differences are marginal – the new car is three-tenths slower to 62mph (at 8.2sec) and three digits slower flat out (as if it matters).

The emissions and economy figures are even more impressive – the 320d ED manages 68.9mpg on the combined cycle and only emits 109g/km, compared to 58.9mpg and 128g/km for the normal car. Buy a 316d and you’ll still only managed 62.8mpg and 118g/km. That means the 320d Efficient Dynamics driver will only pay £35 a year in tax, and face a meagre 13% benefit-in-kind. So the UK is expected to take around 60% of production, and it should account for 30-50% of 320d sales in Blighty.

>> Click 'Next' to read the CAR verdict of the BMW 320d

What’s the new BMW 320d ED like on the road?

Like a regular 320d. There’s the same smooth, accurate steering and thin rim which makes the Three such a joy to drive. And although the suspension has been dropped by 15mm, it’s only a reduction in height rather than an M Sport kit slung on with stiffer springs so the ride doesn’t suffer.

The engine tweaks don’t intrude either. The Efficient Dynamics Three loses a little in the mid-range on paper but in the real world there’s still 265lb ft spread from 1750-3000rpm to make overtaking relatively easily, and you’ll be trying very hard to spot the difference between this and the regular 320d.

The fancy flywheel does make a difference, dampening the vibrations so you’re happier to use lower revs and a higher gear. This also means the gearshift indicator points can be set lower, and although we weren’t trying too hard to be green the trip computer was still claiming over 58mpg.

Will my neighbour know I’m going green?

No, because the only visual difference you’ll notice compared to the standard 320d SE are the inch-smaller alloys and a few minor Efficient Dynamics badging. It’s the familiar 3-series you’ll spot on almost every road in Britain, and in line with 2008’s mid-life facelift there’s LED rear lights, revised front and rear bumpers and a more contoured bonnet. There’s also the latest version of iDrive with shortcut buttons around the main dial.

Even the price is the same – BMW isn’t charging a premium for this car so you’ll pay £26,680 and still get two-zone air-con, rear parking sensors and a multi-functional leather wheel. The only thing you can’t order is the M Sport kit, but there’s nothing stopping you buying an aftermarket set of bigger BMW wheels and still having 109g/km and 68.9g/km on paper.

Verdict

Of course the real-world, day-to-day test will almost certainly reveal that the 320d Efficient Dynamics can’t match its claims figures. Then again, no car ever does and while European governments continue to tax motorists on their vehicle’s CO2 outputs this new BMW makes perfect sense for fleet buyers and those who want to make a difference to their CO2 output. And unless you’re set on having an M Sport-spec 320d then we see no reason not to opt for the Efficient Dynamics model.